CNNMoney recently received a flood of e-mails from readers complaining about the impact of trial modifications on their credit reports.

To be sure, many people who apply for the president's plan are already delinquent in their mortgage payments, which wrecks their credit backgrounds. And obtaining a trial modification should affect borrowers' scores because it shows they cannot meet their original obligation, experts said.

But being in a months-long trial period may only add to the pain.

Jason Axelrod learned that the hard way.

Axelrod, a municipal employee who lives outside Chicago, entered a trial mortgage modification program this spring.

He had not fallen behind in his mortgage, but he was finding it harder to make ends meet after his overtime was cut and his property taxes skyrocketed. Told it would not hurt his coveted 750 score, Axelrod secured a $565 reduction in his monthly payments.

Eight months later, Axelrod is still stuck in the trial modification, trying to satisfy his loan servicer's endless requests for documents.

And to his horror, his credit score has plummeted to 644.

"It's completely destroyed my credit," said Axelrod. "If I had known it would affect my score, I would have never entered the program."

Representatives at JPMorgan Chase (JPM, Fortune 500), which services Axelrod's loan, are instructed to tell applicants that entering a modification could impact their credit histories, a bank spokeswoman said.

Despite his weakened credit score, there is at least some good news for Axelrod: After being contacted by CNNMoney.com, JPMorgan Chase said his permanent modification had been approved.

Credit reporting guidelines

Under the president's plan, troubled borrowers can have their monthly mortgage payments reduced to 31% of their pre-tax income.

Homeowners are first put in a trial modification for several months to prove they can handle the new commitment and to give the bank time to collect the necessary income and hardship verification documents.

During this period, industry guidelines call for loan servicing companies to reportborrowers to the credit bureaus according to their status before they entered the modification - either current or the number of days delinquent.

However, borrowers' accounts are also designated with a code indicating they are in a partial payment plan.

The coding alone can impact credit scores, which measure a consumer's financial health and range from 300 to 850 under the FICO system. The severity depends on how many payments the borrower missed before entering the program. Those who were current in their mortgages could see their scores fall up to 100 points, according to the Treasury Department.

Just what banks are reporting to the credit bureaus remains a matter of some debate. Some servicers have been inconsistent in following the guidelines, according to a Treasury official. Also, they don't always report that their current borrowers have entered modification plans.

Some 24,000 trial modifications were given to those still current with their payments, as of early September. A total of 366,000 trial modifications were in effect at that time. The total number has since risen to just under 700,000, as of the end of November.

JPMorgan Chase, Wells Fargo (WFC, Fortune 500) and Citigroup (C, Fortune 500), which are among the nation's largest servicers, declined to be interviewed for this article. A Bank of America (BAC, Fortune 500) spokeswoman said the bank follows industry guidelines.

According to the Mortgage Bankers Association, an industry group, servicers are required to report all information about their clients, including whether they are in modification plans. For seriously delinquent borrowers, this may improve their status somewhat since they will start making payments again.

"If you are in the trial period, over that three month period, you are going to improve your situation in most cases," said Vicki Vidal, the group's associate vice president for government affairs.

Once borrowers receive a permanent modification, their payment status is listed as current. However, the delinquency remains on their credit reports for up to seven years.

On top of that, the longer homeowners are listed as delinquent, the greater the impact on their credit score. That's one reason why servicers should be quicker to convert borrowers from trial modifications to permanent adjustments, said Jan Jones, a housing counselor in Alaska.

Financial institutions have come under fire in recent weeks for dragging their feet in evaluating borrowers for permanent adjustments.

"What's making people upset is the length of time lenders are taking to consider these workout plans," said Jones, who works for Consumer Credit Counseling Service of Alaska.

Axelrod is already feeling the impact of his lower credit score. He ordered a new car this summer, believing it would come with a lower monthly payment. It arrived in mid-December.

But because of his newly blemished credit background, his two credit unions turned him down for a car loan. His dealership told him the best he could get is a 12% rate, a hefty hike from the 4.7% he was paying before.

"This is the biggest nightmare," he said. "My credit is completely useless."